The present invention relates to a brake device for a vehicle and a control method thereof, and particularly to a brake device which includes a hydraulic brake and a regenerative brake for producing a regenerative brake force, and which can distribute a braking force between a hydraulic brake force and the regenerative brake force, and a control method thereof.
As a brake device for a vehicle of the related art, a brake device for a vehicle, which includes both a hydraulic brake for producing a hydraulic brake force using a hydraulic pressure being produced according to a brake operation of a driver, and a regenerative brake for producing a regenerative brake force, and which performs a regenerative cooperation by distributing a braking force between the hydraulic brake force and the regenerative brake force, is known.
An object of the regenerative brake being used for such a brake device for a vehicle is to convert kinetic energy of a vehicle wheel at the time of braking into electrical energy and to effectively use the energy, but a maximum regenerative brake force which can be regenerated by the regenerative brake is limited by a vehicle speed at the time of the vehicle braking, a charging state of a battery or the like. For this reason, it is preferable that a ratio between the braking force produced by the hydraulic brake and the braking force produced by the regenerative brake be changed according to the maximum regenerative brake force, and a proportion of the regenerative brake be increased, from a viewpoint of effective use of energy, even while the hydraulic brake is performed.
For this reason, various methods have been proposed to perform the regenerative cooperation, but in a case where the ratio of the regenerative brake with respect to the braking force is changed, the driver feels discomfort in brake feel. For this reason, as a means of obtaining comfortable brake feel, when the braking is performed by the regenerative brake, brake fluid escapes into a low pressure accumulator via a pressure decreasing valve, and when the hydraulic pressure is increased, the brake fluid is pumped out of the accumulator by a motor pump unit which is electrically controlled (for example, refer to JP-T-2007-500104).